Sheril's post, Chimpanzees Are NOT Pets!, is good. She notes:
1 Chimpanzees are wild animals. Animals that make good PETS like dogs and cats, have been domesticated for [thousands] of years. There has been selection on them against aggression, which is why a dog, unlike a wolf, will not automatically tear you to pieces. Anyone who has a pet chimpanzee for long enough will eventually no longer be able to control them and will either get a body part bitten off or will have to use extreme force to control them. Chimps live to be 50 years old and grow almost as big as a human male. They have extremely powerful muscles and are 5-10 stronger than a heavy weight boxer.
There is some more nuance to this. 1) Dog breeds differ in temperament, so not all are equally fluent in the ways of man 2) Dogs can read human faces:
Dogs are more skillful than great apes at a number of tasks in which they must read human communicative signals indicating the location of hidden food. In this study, we found that wolves who were raised by humans do not show these same skills, whereas domestic dog puppies only a few weeks old, even those that have had little human contact, do show these skills. These findings suggest that during the process of domestication, dogs have been selected for a set of social-cognitive abilities that enable them to communicate with humans in unique ways.
The domestic dog has been selected to be our best friend. Cats are perhaps a different matter, but due to their relative aloofness and small size "misunderstandings" are less problematic than they would be with a Great Dane. In any case, H. sapiens is a relatively gracile ape, our closest relatives the chimpanzees can tear us apart, quite literally. Travis, the chimp who maimed a woman and was killed clearly had a history of acting out. His owner also seemed to have an inappropriate emotional relationship to him.
